Head suspension having tapered processing holes and method for aligning tooling during suspension manufacture

ABSTRACT

A head suspension for a rigid disk drive comprising one or more tapered processing holes in the load beam. The tapered processing holes can be located in the rigid region, the flexure or the mounting region. The tapered processing holes have a first diameter at a first surface of the load beam and a second diameter at a second surface of the load beam, wherein the first diameter is less than the second diameter. A method of processing a head suspension for a rigid disk drive is also disclosed. A processing tool is operatively engaging with the tapered processing hole to perform one of mechanically or optically locating, measuring. mounting, and/or aligning a suspension arm or components thereof.

This application claims the benefit of U.S. Provisional Application Ser.No. 60/131,096 filed Apr. 26, 1999.

FIELD OF THE INVENTION

The present invention is directed to tapered processing holes for a headsuspension in a rigid disk drive and to a method for processing headsuspensions using the tapered processing holes.

BACKGROUND OF THE INVENTION

In a dynamic rigid disk storage device, a rotating disk is employed tostore information. Rigid disk storage devices typically include a frameto provide attachment points and orientation for other components, and aspindle motor mounted to the frame for rotating the disk. A read/writehead is formed on a “head slider” for writing and reading data to andfrom the disk surface. The head slider is supported and properlyoriented in relationship to the disk by a head suspension that providesboth the force and compliance necessary for proper head slideroperation. As the disk in the storage device rotates beneath the headslider and head suspension, the air above the disk also rotates, thuscreating an air bearing which acts with an aerodynamic design of thehead slider to create a lift force on the head slider. The lift force iscounteracted by a spring force of the head suspension, thus positioningthe head slider at a desired height and alignment above the disk that isreferred to as the “fly height.”

Head suspensions for rigid disk drives include a load beam and aflexure. The load beam includes a mounting region at its proximal endfor mounting the head suspension to an actuator of the disk drive, arigid region, and a spring region between the mounting region and therigid region for providing a spring force to counteract the aerodynamiclift force generated on the head slider during the drive operation asdescribed above. The flexure typically includes a gimbal region having aslider-mounting surface where the head slider is mounted. The gimbalregion is resiliently moveable with respect to the remainder of theflexure in response to the aerodynamic forces generated by the airbearing. The gimbal region permits the head slider to move in pitch androll directions and to follow disk surface fluctuations.

In one type of head suspension, the flexure is formed as a separatepiece having a load beam-mounting region that is rigidly mounted to thedistal end of the load beam using conventional methods such as spotwelds. Head suspensions of this type typically include a load pointdimple formed in either the load beam or the gimbal region of theflexure. The load point dimple transfers portions of the load generatedby the spring region of the load beam to the flexure, provides clearancebetween the flexure and the load beam, and serves as a point about whichthe head slider can gimbal in pitch and roll directions to followfluctuations in the disk surface.

The actuator arm is coupled to an electromechanical actuator thatoperates within a negative feedback, closed-loop servo system. Theactuator moves the data head radially over the disk surface for trackseek operations and holds the transducer directly over a track on thedisk surface for track following operations.

The head suspensions are typically formed from a sheet of metal usingsingle step or multi-step etching procedures, such as disclosed in U.S.Pat. Nos. 4,235,664; 4,251,318; and 5,846,442. The etching proceduregenerally includes coating both sides of the sheet material with a photoresist; locating a photo mask on both sides of the metal sheet; exposingthe photo resist through the photo mask; developing the photo resist andetching the desired feature. flowever, since suspension components aremade by etching simultaneously from both sides of the sheet material,misregistration of the photo mask during exposure causes a shift betweenthe top and bottom of any processing holes in the component.Consequently, the center for the best fit perpendicular cylinder in theprocessing hole may not align with the center of the processing hole.For example, rather than having a center axis perpendicular to thesurfaces of the sheet material, processing holes can be skewed, having across sectional shape of a parallelogram rather than rectangular.Consequently, when such processing holes are engaged with a processingtool, such as an alignment pin, the center line of the processing toolwill be misregistered with respect to the center line of the processinghole.

Therefore, a need exists for improved processing holes for headsuspensions and for an improved method of processing head suspensionsusing such processing holes.

BRIEF SUMMARY OF THE INVENTION

The present invention is directed to a head suspension for a rigid diskdrive comprising one or more tapered processing holes in the load beam.The tapered processing holes can be located in the rigid region, theflexure or the mounting region. The tapered processing holes comprise afirst diameter at a first surface of the load beam and a second diameterat a second surface of the load beam, wherein the first diameter is lessthan the second diameter.

The tapered processing holes are formed by etching. The taperedprocessing holes comprise side walls forming an angle with respect to afirst surface of the load beam of less than about 85 degrees. In oneembodiment, the angle is between about 75 degrees and about 85 degrees.The processing hole will comprise a generally conical or frusto-conicalshape, although the shape may be asymmetrical due processingvariability.

In another aspect of the present invention, a method of processing ahead suspension for a rigid disk drive is disclosed. A head suspensionis provided having a load beam having a mounting region, a rigid regionand a spring region located between the mounting region and rigidregion. The head suspension has at least one tapered processing holecomprises a first diameter at a first surface of the load beam and asecond diameter at a second surface of the load beam, wherein the firstdiameter is less than the second diameter. A processing tool isoperatively engaged with the tapered processing hole to perform one ofmechanically or optically locating, measuring, mounting, and/or aligninga suspension arm or components thereof. A plurality of processingdevices can be operatively engaged with a plurality of taperedprocessing holes.

The processing tool is typically inserted through the first surface intothe tapered processing hole. The processing tool can be a taperedprocessing tool, a straight tool, a machine vision system, or the like.

The tapered processing hole is formed by etching. A photo mask islocated along the first and second surfaces of the load beam prior toetching the tapered processing hole.

The tapered processing hole can be used as a reference point formeasuring locations on the head suspension. For example, anothercomponent can be aligned to the head suspension relative to the locationof the tapered processing hole. Alternatively, a tapered processing holeon another component can be aligned with the tapered processing hole onthe load beam. For example, a tapered processing hole on a flexure canbe aligned relative to the tapered processing hole on the load beam. Inanother embodiment, a processing device is aligned with the taperedprocessing hole on a feature forming tool and a feature is formed in theload beam, such as a dimple on the load beam.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a plan view of a carrier strip having a plurality ofsuspension arms.

FIG. 2 is a perspective view of head suspension assembly in accordancewith the present invention.

FIG. 3 is a schematic illustration of a generic suspension arm.

FIG. 4 is a side sectional view of conventional processing holes formedin the suspension arm of FIG. 3.

FIG. 5 is a side sectional view of tapered processing holes inaccordance with the present invention formed in the suspension arm ofFIG. 3.

FIG. 6 is a side sectional view of misregistration between a processingtool and a conventional processing hole.

FIG. 7 is a side sectional view of registration between a processingtool and a tapered processing hole in accordance with the presentinvention.

FIG. 8 is a graph illustrating symmetry, location and position data fora prior art processing hole.

FIG. 9 is a graph illustrating symmetry, location and position data fora tapered processing hole in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a carrier strip 50 having a plurality of suspensionarms 52. The suspension arms 52 include a series of processing holes 54,55, 56, 58, 60 that were generated as a result of misalignment of thephoto tools. Misalignment of the processing hole 54 is shown by a lackof concentricity between the entrance 62 to the hole 54 along the firstsurface 64 and the exit 66 of the hole 54. The same lack ofconcentricity is illustrated in the processing holes 55, 56, 58, and 60.

FIG. 2 is an exploded, isometric view of a head suspension assembly 10having various tapered processing holes for use with processing tools inaccordance with the present invention, as will be discussed below. Asused herein, “tapered” refers to a hole having an opening along a firstsurface of a sheet material with a diameter greater than the diameter ofthe opening along a second. surface of the sheet material.Alternatively, tapered can be viewed as a shape generally correspondingto a cross-section of a cone, although due to processing variability thetaper of the side walls may not be symmetrical. A “processing hole”refers to any hole used for mechanically or optically locating,measuring, mounting, and/or aligning a suspension arm or componentsthereof A “processing tool” refers to a mechanical or optical mechanismthat uses a processing hole for locating, measuring, mounting and/oraligning a suspension arm or components thereof.

The head suspension assembly 10 includes a load beam 12 with. a flexure16 to which a head slider 20 having a read/write element or head is tobe mounted. The load beam 12 includes a mounting region 14 at a proximalend, a rigid region 22 adjacent to a distal end and a spring region 18between the mounting region and rigid region. Spring region 18 isrelatively resilient and provides a downward bias force at the distaltip of load beam 12 for holding the read/write head near a spinning diskin opposition to an upward force created by an air bearing over thedisk. The flexure 16 is to allow pitch and roll motion of head slider 20and read/write head as they move over the data tracks of the disk. Thehead suspension assembly 10 is typically coupled to the actuator via theactuator arm 32 that is attached to the mounting 14 region of load beam12.

A swage type attachment is commonly used to couple the mounting regionof a load beam to an actuator arm. To swage load beam 12 to actuator arm32, actuator arm 32 and mounting region 14 include apertures 34 and 26,respectively. A base plate 24 having a boss tower 28 with a swage hole30 extending therethrough and, typically, a square flange 36 is weldedor otherwise attached to a bottom face of mounting region 14 of loadbeam 12. Boss tower 28 is then inserted through actuator arm aperture34. A swage ball is then forced through swage hole 30 in boss tower 28causing boss tower 28 to expand in actuator arm aperture 34. Thiscreates a frictional attachment interface between the exterior surfaceof boss tower 28 and the interior surface of actuator arm aperture 34.

The aperture 26 is a tapered processing hole that can optionally be usedto align the head suspension assembly 10 with boss tower 28. In additionto aperture 26, the load beam 12 typically includes one or more taperedprocessing holes 38, 40, 42, 44. The tapered processing hole 38 isuseful for aligning the load beam 12 with the base plate 24 and/oractuator arm 32. The base plate 24 and/or actuator arm 32 may optionallyinclude corresponding processing holes 38 a, 38 b to facilitatealignment.

The load beam 12 also includes one or more tapered processing holes 40near the spring region 18 and one or more tapered processing holes 42,44 near distal end 46. The tapered processing holes 40, 42, 44 can beused to align the load beam 12 with a fixture or with other components,such as the base plate 24, the flexure 16, and/or the slider 20. Theprocessing holes 42, 44 can also be aligned with correspondingprocessing holes 42 a, 44 a on another component, such as flexure 16.Additionally, the tapered processing holes 40, 42, 44 can be used toregister the load beam 12 in a fixture for a feature forming process,such as forming dimple 48 on distal end 46. Any of the processing holes26, 38, 40, 42, 44 can be used as reference locations for measuringfeature locations on the load beam 12.

FIG. 3 is a top schematic view of a suspension arm 80 having processingholes 82, 84, 86. Dimple 88 is located near distal end 90 of thesuspension arm 80. Each of the processing holes 82, 84, 86 has a centralaxis 100, 102, 104, respectively.

FIG. 4 is a side sectional view of a suspension arm 80′ havingprocessing holes 82′, 84′, 86′ formed using conventional photo etchingtechniques. The suspension arm 80′ is aligned with the suspension arm 80to show the relative positioning of the respective processing holes. Asa result of misalignment of the upper and lower photo masks, theprocessing holes 82′, 84′, 86′ are slanted or skewed with respect tofirst surface 92′. That is, the centerline of the processing holes 82′,84′, 86′ are not perpendicular to the first surface 92′. A best fitcylinder located in the processing holes 82′, 84′, 86′ would have centeraxes 94′, 96′, 98′, respectively, offset from the center axes 100, 102,104 of the processing holes 82, 84, 86. The offset between the axes 94′,96′, 98′ with respect to the axes 100, 102, 104, respectively,represents misregistration of the processing holes 82′, 84′, 86′. Thismisregistration will occur regardless of which surface of the headsuspension 80′ is used for registering with processing tools.

FIG. 5 illustrates an alternate cross section of a head suspension 80′having a series of tapered processing holes 82″, 84″, 86″. The centeraxes of a best fit cylinder located in the processing holes 82″, 84″,86″ will correspond with the axes 100, 102, 104 of the processing holes80, 84, 86 of the head suspension 80.

The processing holes 82″, 84″ and 86″ have a smaller diameter 106″,108″, 110″ at the first surface 92″, respectively, than the diameters112″, 114″, 116″ along the second surface 93″. The etched-throughprocessing holes 82″, 84″, 86″ also have sloped side surfaces 82 a″, 82b″, 84″a, 84″b, 86″a, 86″b so that even if the top and bottom phototools are misregistered, only the small diameter holes 106″, 108″, 110″along the first surface 92″ are used as the controlling feature of theprocessing hole 82″, 84″, 86″. Consequently, the center of the best fitperpendicular cylinder will align with the center of the taperedprocessing holes 82″, 84″, 86″ along axes 100, 102, 104. The sloped sidesurfaces 82 a″. 82 b″, 84″a, 84″b, 86″a, 86″b are not necessarilysymmetrical due to misalignment of the photo tools during the step ofexposing the photo resist through the photo tools. That is, the slope ofa given side surface may vary around the diameter of the processing hole82″, 84″ and 86″.

FIG. 6 is a side sectional view of a processing tool 120, such as analignment pin, engaged with a processing hole 122 and a load beam 124 ofa head suspension. The processing hole 122 was formed using conventionaltechniques, As a result of misalignment of the upper and lower phototools, the center line 126 of the processing hole 122 is offset by adistance 128 from center line 130 of the alignment pin 120. The distance128 represents that quantity of misregistrition of the alignment pin 120relative to the load beam 124. Since the diameter of the processing hole122 is the same along both the first surface 132 and the second surface134, the indicated misalignment 128 would be present regardless ofwhether the alignment pin 120 was inserted through the first surface 132or the second surface 134.

FIG. 7 illustrates the alignment pin 120 engaging with a processing hole140 formed in a load beam 142 in accordance with the present invention.The processing hole 140 has tapered side walls 144 forming an angle 145with the first surface 146 of less than about 85 degrees. In oneembodiment, the angle 145 is between about 75 degrees and about 85degrees. The diameter of the processing hole 140 along first surface 146is smaller than the diameter along the second surface 148. Consequently,centerline 150 of the processing hole 140 is co-linear with centerline130 of the alignment pin 120. Although the alignment pin 120 isillustrated as tapered, the present tapered processing hole 140 willalso achieve accurate registration with a cylindrical alignment pin.

EXAMPLE

Head suspensions for disk drives typically include a stampedhemispherical shaped feature or dimple in the distal end of theloadbeam. In order accurately stamp the dimple, the stamping die locatesthe part datum structure by using one or more of the processing holes inthe head suspension. Once the part is located, the die stamps in thedimple feature. The dimple is then measured relative to its datumstructure using a vision system. The vision system measures X and Y axisshifts in the stamped dimple verses the true datum structure—where the Xaxis is referred to Symmetry; the Y axis is referred to Location, and((X²+y²)^(0.5))*2 is referred as Position.

FIG. 8 shows the Symmetry, Location and Position data for model QM headsuspensions available from Hutchinson Technology, Inc. with non-taperedprocessing holes in the load beam. Each letter A-R on the horizontalaxis corresponds to a strip containing twelve head suspension.Therefore, FIG. 8 contains data for a total of 192 head suspension. Onemeasurement is taken for each head suspension. Each data point is anaverage of the twelve measurements taken for a given strip. The Positiondata on the sample with non-tapered processing holes vary from about0.006 millimeters to about 0.020 millimeters.

FIG. 9 shows the Symmetry, Location and Position data for the same modelQM head suspensions available from Hutchinson Technology, Inc. withtapered processing holes in the load beam. Each letter A-R on thehorizontal axis corresponds to a strip containing twelve headsuspension. One measurement is taken for each head suspension. Each datapoint is an average of the twelve measurements taken for a given strip.The Position data on the sample with tapered processing holes show alower level of variability in the range of about 0.011 millimeters toabout 0.014 millimeters. The tapered processing holes lower thevariability in the Position data.

All patents and patent applications disclosed herein, including thosedisclosed in the background of the invention, are hereby incorporated byreference. Although the present invention has been described withreference to preferred embodiments, workers skilled in the art willrecognize that changes may be made in form and detail without departingfrom the spirit and scope of the invention. In addition, the inventionis not to be taken as limited to all of the details thereof asmodifications and variations thereof may be made without departing fromthe spirit or scope of the invention.

What is claimed is:
 1. A head suspension for a rigid disk drivecomprising: a load beam having a mounting region, a rigid region and aspring region located between the mounting region and rigid region, andone or more etched, tapered processing holes in the load beam.
 2. Thehead suspension of claim 1 wherein the tapered processing hole comprisesone or more tapered processing holes located in the rigid region.
 3. Thehead suspension of claim 1 wherein the head suspension includes aflexure comprising one or more tapered processing holes.
 4. The headsuspension of claim 1 wherein the tapered processing hole comprises oneor more tapered processing holes located in the mounting region.
 5. Thehead suspension of claim 1 wherein the tapered processing hole comprisesone or more tapered processing holes in the spring region.
 6. The headsuspension of claim 1 wherein the tapered processing hole comprises afirst diameter at a first surface of the load beam and a second diameterat a second surface of the load beam, wherein the first diameter is lessthan the second diameter.
 7. The head suspension of claim 1 wherein thetapered processing hole comprises a processing bole formed bysimultaneously etching a first surface and a second surface of the loadbeam.
 8. The head suspension of claim 1 wherein the tapered processinghole comprises side wall forming an angle with respect to a firstsurface of the load beam of less than about 85 degrees.
 9. The headsuspension of claim 1 wherein the tapered processing hole comprises sidewall forming an angle with respect to a first surface of the load beamof about 75 degrees to about 85 degrees.
 10. A head suspension for arigid disk drive comprising: a load beam having a mounting region, arigid region and a spring region, located between the mounting regionand rigid region and one or more tapered processing holes in a flexure.11. The flexure of claim 10 wherein the tapered processing holecomprises a first diameter at a first surface of the flexure and asecond diameter at a second surface of the flexure, wherein the firstdiameter is less than the second diameter.
 12. A method of processing ahead suspension for a rigid disk drive comprising the steps of:providing a head suspension comprising a load beam having a mountingregion, a rigid region and a spring region located between the mountingregion and rigid region, the head suspension having at least one etched,tapered processing hole comprising a first diameter at a first surfaceof the load beam and a second diameter at a second surface of the loadbeam, wherein the first diameter is less than the second diameter; andoperatively engaging a processing device with the tapered processinghole.
 13. The method of claim 12 wherein the step of operativelyengaging the processing device comprises the step of inserting aprocessing tool through the first surface into the tapered processinghole.
 14. The method of claim 13 wherein the processing tool comprises atapered processing tool.
 15. The method of claim 12 wherein the step ofoperatively engaging a processing device comprises the step of operatinga machine vision system to determine a center of the tapered processinghole.
 16. The method of claim 12 comprising the step of forming thetapered processing hole by simultaneously etching the first surface andthe second surface of the load beam.
 17. The method of claim 12comprising the step of locating a photo mask along the first and secondsurfaces of the load beam prior to etching the tapered processing hole.18. The method of claim 12 comprising the step of aligning anothercomponent to the head suspension relative to the location of the taperedprocessing hole.
 19. The method of claim 12 comprising the step ofaligning a tapered processing hole on another component relative to thetapered processing hole on the load beam.
 20. The method of claim 12comprising the step of aligning a tapered processing hole on a flexurerelative to the tapered processing hole on the load beam.
 21. The methodof claim 12 comprising the step of operatively engaging a plurality ofprocessing devices with a plurality of tapered processing holes.
 22. Themethod of claim 12 comprising the steps of: aligning the taperedprocessing hole with a processing device on a feature forming tool; andforming a feature in the load beam.
 23. The method of claim 22 whereinthe step of forming a feature comprises forming a dimple in the loadbeam.
 24. A method of processing a flexure for a head suspension in arigid disk drive comprising the steps of: providing a flexure having atleast one tapered processing hole comprising a first diameter at a firstsurface of the flexure and a second diameter at a second surface of theflexure, wherein the first diameter is less than the second diameter;and operatively engaging a processing device with the tapered processinghole.
 25. The method of claim 24 wherein the step of operativelyengaging the processing device comprises the step of inserting aprocessing tool through the first surface into the tapered processinghole.
 26. The method of claim 24 wherein the step of operativelyengaging a processing device comprises the step of operating a machinevision system to determine a center of the tapered processing hole. 27.The method of claim 24 comprising the step of forming the taperedprocessing hole by simultaneously etching the first surface and thesecond surface of the flexure.
 28. The method of claim 24 comprising thestep of aligning a tapered processing hole on a load beam relative tothe tapered processing hole on the flexure.
 29. A head suspension for arigid disk drive comprising: a load beam having a mounting region, arigid region and a spring region located between the mounting region andrigid region, and one or more tapered processing holes in the rigidregion.
 30. A head suspension for a rigid disk drive comprising: a loadbeam having a mounting region, a rigid region and a spring regionlocated between the mounting region and rigid region, and one or moretapered processing holes in the spring region.